Polypeptides and other foreign substances, particularly biologically active substances, are transferred into the cells of humans and other mammals, etc., (eukaryotic cells) to change the characteristics or to improve and enhance the function of the cells (as well as the tissues and organs comprising the cells).
For example, Patent Document 1 discloses a transcellular carrier peptide for transferring polypeptide, DNA or another foreign substance into a cell. This patent indicates that a polypeptide, DNA, or other biologically active substance can be transferred into a cell with high efficiency by using a carrier peptide conjugate comprising a transcellular carrier peptide linked to a xenogenic polypeptide, DNA, and the like.
Still, a method is needed for changing the characteristics and improving (or enhancing) the function of the cells by easily transferring a full-length polypeptide with a relatively large molecular weight as the foreign substance (biologically active substance) to be transferred into a target cell without the use of special equipment.
Alternatively, in place of transferring a polypeptide or a full-length protein, a method is needed wherein the focus is placed on the specific function of the polypeptide, and a partial amino acid sequence that is the minimum unit capable of expressing that function, i.e., an amino acid sequence (foreign substance) constituting a peptide motif, is transferred efficiently into the cell.
For example, Patent Document 2 discloses part of a peptide chain (amino acid sequence) found in the SOCS protein and other proteins of the same family (hereinafter, “SOCS proteins”) that is a motif wherein the amino acid sequence constituting all or part of the specific region called the “BC box,” which is believed to bind to the elongin BC complex, has a high level of neuronal differentiation inducing activity on somatic stem cells. Patent Document 2 also discloses that transferring the motif into mammalian somatic stem cells can induce them to differentiate into nerve cells.